[go][client] Import "time" package if property is oneOf and contains time.Time

[cmaan]

Fix an issue with go client generator, where "time" import is missing if the time.Time type is wrapped in oneOf

    ObjectAttributeValue_value:
      oneOf:
      - type: string
      - format: date-time
        type: string

(via https://developer.atlassian.com/cloud/insight/swagger.v3.json)

openapi-codegen generate -i https://developer.atlassian.com/cloud/insight/swagger.v3.json -g go -o cloud-insight-test/
cd cloud-insight-test/ && go get && go build

Without fix:

# github.com/GIT_USER_ID/GIT_REPO_ID
./model_object_attribute_value_value.go:21:12: undefined: time
./model_object_attribute_value_value.go:32:45: undefined: time
./model_object_attribute_value_value.go:88:21: invalid operation: src.TimeTime != nil (operator != not defined on untyped nil)
./model_object_attribute_value_value.go:104:21: invalid operation: obj.TimeTime != nil (operator != not defined on untyped nil)

With fix the client builds without error.

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh
  

  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  For Windows users, please run the script in Git BASH.
• File the PR against the correct branch: master (6.1.0) (minor release - breaking changes with fallbacks), 7.0.x (breaking changes without fallbacks)
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

@antihax @grokify @kemokemo @jirikuncar @ph4r5h4d

[wing328]

Tested locally and the result is good:

--- PASS: TestPlaceOrder (0.05s)
=== RUN   TestCreateUser
--- PASS: TestCreateUser (0.02s)
=== RUN   TestCreateUsersWithArrayInput
--- PASS: TestCreateUsersWithArrayInput (0.01s)
=== RUN   TestGetUserByName
--- PASS: TestGetUserByName (0.03s)
=== RUN   TestGetUserByNameWithInvalidID
--- PASS: TestGetUserByNameWithInvalidID (0.01s)
=== RUN   TestUpdateUser
--- PASS: TestUpdateUser (0.03s)
PASS
ok  	github.com/OpenAPITools/openapi-generator/samples/openapi3/client/petstore/go	42.953s
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  50.220 s
[INFO] Finished at: 2022-10-17T17:17:14+08:00
[INFO] ------------------------------------------------------------------------

[wing328]

FYI. I've added a tests via #13713

[wtrocki]

@cmaan This PR seem to have fixed oneOf but in result allOf are now broken. Adding this now (along with more tests for imports)

[wtrocki]

Creating PR. See #14121